Conventionally, there has been known a technique that switches a communication mode from wire communication to wireless communication (see Japanese Laid-Open Patent Application Nos. 09-305508 and 08-204777).
Further, there has been conventionally known a data transmission system including: a local unit that transmits an analog video signal (i.e., an RGB signal) output from a computer and a response signal relating to the operation of a keyboard and a mouse to a remote place with a Cat5 (i.e., category 5) cable including four pairs of signal lines; and a remote unit that transmits an operation signal of the keyboard and the mouse to the local unit and receives the above-mentioned analog video signal and the above-mentioned response signal (see Japanese Laid-Open Patent Application No. 2004-356939).